sql server2005新特性

sql server2005新特性

sql server2005新特性
先来个例子

SELECT  
     YEAR (BirthDate),
    ROW_NUMBER()  OVER ( ORDER   BY   YEAR (BirthDate))  AS   ' RowNumber ' , /*  按年产生一个唯一的序号  */
    ROW_NUMBER()  OVER (PARTITION  BY   YEAR (BirthDate)  ORDER   BY  BirthDate)  AS  RowNumberPartition,  /*  每年产生一个唯一的序列  */
    RANK()  OVER ( ORDER   BY   YEAR (BirthDate))  AS   ' Rank ' ,  /*  产生一个非紧密排名  */
    DENSE_RANK()  OVER ( ORDER   BY   YEAR (BirthDate))  AS   ' Dense_Rank ' ,  /*  产生一个紧密排名  */
    NTILE( 10 )  OVER ( ORDER   BY  BirthDate  DESC )  AS   ' ntile '   /*  将结果分成10个组  */
FROM  HumanResources.Employee
ORDER   BY  BirthDate

看看新的排序函数如何解决SQL server 2000中不方便解决的问题

-- 按BirthDate排序，取第10条到20条的数据 (这一定是最激动人心的新特性，哈哈)
SELECT  BirthDate  FROM  
(
     SELECT
        ROW_NUMBER()  OVER ( ORDER   BY  BirthDate)  AS  a,BirthDate
     FROM  HumanResources.Employee
)  AS  a
WHERE  a  BETWEEN   10   AND   20

-- 将数据分成十份，取第三份
SELECT
    BirthDate
FROM
(
SELECT  
    NTILE( 10 )  OVER ( ORDER   BY  BirthDate  DESC )  AS  a,BirthDate
FROM  HumanResources.Employee
)  AS  a
WHERE  a  =   3

再来看看如何用新的排序函数解决以前在SQL server 2000中的问题

--  出生的员工最多的一年出生多少员工（有点）
/*  SQL server 2000  */
SELECT   MAX (a)
FROM
(
SELECT   COUNT (EmployeeID)  AS  a  FROM  HumanResources.Employee  GROUP   BY   YEAR (BirthDate)
)  AS  a

/*  SQL server 2005   */
SELECT   MAX (a)
FROM
(
SELECT  
    ROW_NUMBER()  OVER (PARTITION  BY   YEAR (BirthDate)  ORDER   BY  BirthDate)  AS  a
FROM  HumanResources.Employee
)  AS  a

--  出生日期涵盖了多少年
/*  SQL server 2000   */
SELECT   COUNT ( DISTINCT   YEAR (BirthDate))  FROM  HumanResources.Employee

/*  SQL server 2005  */
SELECT   MAX (a)
FROM
(
SELECT  
    DENSE_RANK()  OVER ( ORDER   BY   YEAR (BirthDate))  AS  a
FROM  HumanResources.Employee
)  AS  a

--  显示前10%的数据
/*  SQL server 2000   */
SELECT   TOP   10   Percent  BirthDate  FROM  HumanResources.Employee

/*  SQL server 2005   */
SELECT
    BirthDate
FROM
(
SELECT  
    NTILE( 10 )  OVER ( ORDER   BY  BirthDate  DESC )  AS  a,BirthDate
FROM  HumanResources.Employee
)  AS  a
WHERE  a  =   1